Custom Header Specs / Design

[Cheromaniac]

The firing order is 1-5-3-6-2-4 with each cylinder firing 120 degrees apart. From that, you can see that the header primaries should be grouped as 1,2,3 and 4,5,6.

[TheDarkSideofWill]

Or maybe it's 1-3-2 & 5-6-4.

[Plechtan]

Once you have the design, your problem will be to get the header made. You can get a header flange from Hesco, who gets it from Borla. You may be able to purchase it directly from Borla, I don't know. Kromer Kraft in PA will make you a custom port matched CNC flange, but you will have to send him your head unless you just want a standard flange. I see you are in Norcal, The closest place i know that does quality work is SPD exhaust in Sunco Rancho Cordova.

Hope this helps.

[SIXPAK]

Groupings are done 1,2,3 and 4,5,6. Using this scenario look at the numbers to the right and follow the firing order. Following your suggested pairings does not allow proper scavenging between cylinders.

my suggestion was more of an example and less of a idea.

i see them 123/456 all the time and wondered if it was the best scavenge or just lazy/easy manufacture.

i didnt see anything to the right and didnt understand you about following the firing order. just another example of me trying hard to learn and all you group members doing an excellent job of steering me straight.
I truly thank you!
Mark

SORRY CC, meant to say left sometimes I type with with my head up my butt. Cheromaniac put it well in his above post.

[1bolt]

One thing to keep in mind on "wave tuning" is that doing it properly and actually GETTING the wave you're shooting for requires actual track testing and will only be effective in a narrow RPM range even with it dialed in. In the end basic inertia (scavenging) seems to be both more significant and easier to tune for.... I base this on in-depth reading over at speedtalk, not any expertise on my own part. Basically it's for racing where getting an extra 2 ft-lbs of torque over a 300 RPM niche might mean faster laps.

So with that in mind, you want the longest primaries you can fit, or reasonably afford to have custom built... Tube size on most 4.0 headers is 1.5" OD Effectively 58" inches of primary length is the most you'll want to go. Somewhere around 38" is fairly optimal, longer than that adds power still but starts getting into diminishing returns. In other words at some point after 38" you're playing a game of weighing the cost of an increasingly complicated snake nest of tubes, and the half point of torque you might gain by adding a couple more inches to the primaries...

[Biggrnjeep97]

If it helps any: I called Banks to see if they'd sell only the SS exhaust flange. I believe its .375 thick and 304L SS. They said theyd sell it for ~$150. IIRC, i think its also waterjet cut so the SS is in tip top shape for welding.
-Will